Living at highest latitudes—the meiofauna of the Langseth Ridge (Arctic Ocean)—taxa composition, distribution, diversity and comparison with other marine regions

Abstract The expedition PS101 of RV POLARSTERN in 2016 offered the first opportunity for quantitative comparisons of metazoan meiobenthos of three different seamounts along the Langseth Ridge (High Arctic). Three hypotheses were to be tested: the meiobenthic communities of the studied elevations do not differ: ( H 0 1 ) in their composition and taxa diversity, ( H 0 2 ) with respect to different substrate types, and ( H 0 3 ) from communities of other seamounts. The comparisons led to the acceptance of H 0 1 , but to the rejection of H 0 2 , as the three substrate types investigated (spicule-tube mat, underlying sediment, bare sediment) do not harbour a uniform meiofaunal community, but different assemblages, both in terms of taxa composition, abundance and diversity. The examination of H 0 3 could only be carried out qualitatively and could therefore only reveal tendencies. The comparison with the 11 Atlantic and Mediterranean seamounts and islands examined so far showed that seven of the 27 recorded major taxa occur on all elevations. This contrasts with ten taxa that were only found sporadically (on one to four elevations) and 12 taxa that were found on five to eleven seamounts/islands. An additional latitudinal and bathymetric comparison based on densities of dominating Nematoda and Copepoda from the Atlantic High Arctic to the High Antarctic (including the eastern Mediterranean and deep-sea regions) revealed that the polar regions are characterised by distinctly higher densities of individuals than lower latitudes, and that the summits/sublittoral of the studied seamounts and islands can by no means be regarded as “oases” in a hostile deep sea surrounding them.